1. Field of the Invention
The present invention generally relates to a shock wave generating apparatus capable of disintegrating an article, e.g., cancer cell, and a concretion within a biological object under medical examination, by utilizing focused energy of shock waves. More specifically, the present invention is directed to a shock wave generating apparatus capable of setting a movement direction for a shock wave generating source for its focus to be within an ultrasonic tomographic image plane formed by an ultrasonic probe.
2. Description of the Related Art
Various types of shock wave generating apparatuses have been proposed in, for instance, Japanese KOKAI (Disclosure) patent application No. 62-49843 (1987).
In FIG. 1, there is shown, as a sectional view, an ultrasonic wave applicator 1 of one conventional shock wave generating apparatus.
The construction of this ultrasonic wave applicator 1 is as follows. A through hole having a predetermined shape is formed in a center portion of this applicator 1. A vibrating element (e.g., piezoelectric transducer element) 2 is spherically formed and backing material 3 is uniformly adhered to a rear surface of this spherical vibrating element 2. An imaging ultrasonic probe 4 is positioned in such a manner that a transmitting/receiving wave front (ultrasonic array) 4a is located at the curved surface identical to the shock wave transmitting/receiving wave front of the vibrating element 2, or at the rear side of the transducer for the, last-mentioned wave front. Furthermore, this ultrasonic wave applicator 1 includes a water bag 5 containing water as a coupling medium for the ultrasonic wave. Reference numeral 6 indicates a biological body under medical examination.
Referring now to FIGS. 2 and 3A to 3D, a description will be provided for a means for identifying a position of an article to be disintegrated, e.g., a concretion or calculus positioned within the biological body 6 by employment of the above-described conventional ultrasonic applicator 1 shown in FIG. 1. That is to say, this implies a means for discovering the actual position of the concretion within the biological body 6 and for making the focal point of the shock wave coincident with the actual concretion position. As shown in FIG. 2, the conventional ultrasonic applicator 1 supported on a supporting member 7 is moved within an X-Y plane over the biological body 6 mounted on a couch 8. This moving operation is controlled by a joy stick 9. A sector-formed ultrasonic beam is projected from the ultrasonic probe 4 employed within the applicator 1, so that a B-mode ultrasonic image (i.e., slice image) of the biological body 6 is formed in the known ultrasonic image forming method and then displayed on a television (TV) monitor 10.
An operator manipulates a joy stick 9 while observing the CT image or B-mode tomographic image displayed on the TV monitor 10. For instance, FIG. 3A represents a screen of the TV monitor 10, on which no concretion to be disintegrated within the biological body 6 is discovered, or appears. When the ultrasonic probe 4 is moved by the operator and the concretion is captured by the ultrasonic probe 4, an image 11 of the concretion is displayed on the TV monitor 10 as shown in FIG. 3B. Subsequently, as represented in FIG. 3C, the ultrasonic applicator 1 is moved in such a manner that the image 11 of the concretion to be disintegrated is positioned at a center of the screen on which a marker 12 to indicate a focal point of a shock wave is also displayed. Then, as shown in FIG. 3D, the ultrasonic applicator 1 is moved downwardly in such a way that the concretion image 11 is moved toward a higher direction of the TV monitor 10 so as to be coincident with the position of the focal point marker 12. As a result, the position of the concretion within the biological body 6 may be identified by the focal point of the shock wave.
As apparent from the foregoing, since the conventional means for identifying the article to be disintegrated is used for the ultrasonic diagnostic apparatus as an imaging means for tissue within a biological body, such an ultrasonic identifying means has a particular advantage in that, for instance, a gallstone mainly containing cholesterol, and soft tissue can be visualized, as compared with the use of X-ray diagnostic apparatus. However, ultrasonic diagnostic apparatus functioning as concretion identifying means has the following drawbacks. That is, since generally, an ultrasonic diagnostic apparatus is for obtaining a two-dimensional CT image of a biological body parallel to an array direction of transducer elements just under an ultrasonic probe, it is rather difficult to identify a position of an article to be disintegrated, as compared with an X-ray diagnostic apparatus for convoluting three-dimensional images along a depth direction of the biological body so as to acquire a two-dimensional image.
That is to say, an article to be disintegrated is continuously displayed on a TV monitor of an X-ray diagnostic (fluoroscopic) apparatus when this article is present within a field of view, whereas an article to be disintegrated is displayed on a TV monitor of an ultrasonic diagnostic apparatus only when this article is positioned on a tomographic image plane (slice plane) produced by way of an ultrasonic probe. As a consequence, in case an article to be disintegrated is discovered from a slice plane produced by way of an ultrasonic probe by an operator and then an image of this article is in coincidence with a focal point marker of a disintegrating shock wave displayed on a monitor screen, this article's image may disappear from the monitor screen of the ultrasonic diagnostic apparatus unless a source of an ultrasonic shock wave is moved along a direction coincident with the above-described slice plane. Under these circumstances, the conventional identifying operation for the position of the article to be disintegrated becomes very difficult, because the shock wave generating source must be transported in such a manner that the article to be disintegrated never disappears from the ultrasonic slice image produced by way of the ultrasonic probe.
The present invention has been made in an attempt to solve the above-described problems and therefore has the object of providing a shock wave generating apparatus capable of simply identifying a position of an article to be disintegrated on a ultrasonic slice plane displayed on a monitor screen. More specifically, another object of the present invention is to provide such a shock wave generating apparatus that when a focal point of a shock wave generating source is made coincident with an image of an article to be disintegrated on a monitor screen of an ultrasonic diagnostic apparatus after the image of this article has been displayed on this monitor screen, a movement (transport) direction for the generating source can be automatically for its focus to be within the tomographic image plane of the ultrasonic probe.